19-nor-vitamin D.sub.3 compounds with calcemic activity

A method of treating metabolic bone disease where it is desired to maintain or increase bone mass comprising administering to a patient with said disease an effective amount of a compound having the formula:

• ##STR6## where X.sup.1 and X.sup.2, which may be the same or different, are each selected from the group consisting of hydrogen and a hydroxy-protecting group, and where the group R is represented by the structure:
• ##STR7## where the stereochemical center at carbon 20 may have the R or S configuration, and where Z is selected from Y, --OY, --CH.sub.2 OY, --C.dbd.CY and --CH.dbd.CHY, where the double bond may have the cis or trans geometry, and where Y is selected from a radical of the structure:
• ##STR8## where m and n, independently, represent the integers from 0 to 5, where each of R.sup.1 and R.sup.2, independently, is selected from hydrogen, deuterium, deuteroalkyl, hydroxy, protected hydroxy, fluoro, trifluoromethyl, and C.sub.1-5 -alkyl, which may be straight chain or branched and, optionally substituted with a hydroxy or protected-hydroxy substituent, and where each of R.sup.3 and R.sup.4, independently, is selected from C.sub.2-5 alkyl, which may be straight-chain or branched, and optionally substituted with a hydroxy or protected-hydroxy substituent, and where R.sup.1 and R.sup.2, taken together, represent an oxo group, or an alkylidene group, .dbd.CR.sup.2 R, or the group --(CH.sub.2).sub.p where p is an integer from 2 to 5, and where R.sup.3 and R.sup.4, taken together, represent the group --(CH.sub.2).sub.q --, where q is an integer from 2 to 5, and where R.sup.5 represents hydrogen, hydroxy, protected hydroxy, or C.sub.1-5 alkyl and wherein any of the CH-groups at positions 20, 22, or 23 in the side chain may be optionally substituted by a nitrogen, and where any of the groups --CH(CH.sub.3)--, --CH.sub.2 --, or --CH(R.sup.2)-- at positions 20, 22, and 23, respectively, may be optionally substituted by an oxygen or sulfur.